Sewing machine with hook timing and skip stitch mechanisms

ABSTRACT

A sewing machine, particularly of the zigzag stitch type in which the needle bar gate is pivotably mounted in the frame of the machine and carries a needle bar and needle mounted thereon for endwise reciprocation and vibratory movement transverse to the line of stitches being produced. The penetration of the needle is co-ordinated with the vibratory movement of the needle bar gate by the provision of an eccentric member co-operable with the gate and with a latch member carried by the needle bar, pivotal movement of the gate effectuating rotation of the eccentric member and linear displacement of the latch member. Means are also provided which co-operate with the latch member for effecting skip stitching.

[ 1 Dec. 18, 1973 SEWING MACHINE WITH HOOK TIMING AND SKIP STITCH MECHANISMS [75] Inventor: Kenneth D. Adams, Madison, NJ.

[73] Assignee: The Singer Company, New York,

[22] Filed: Dec. 13, 1972 [21] Appl. N0.: 314,647

[52] US. Cl. ..112/158 R, 112/182, 112/221 [51] Int. Cl D051) 3/02 [58] Field of Search 112/79, 158 R, 158 A,

[56] References Cited UNITED STATES PATENTS 2,003,461 6/1935 Pearson 112/221 X 2,318.200 5/1943 Cobble et al. 112/221 X 2,662,495 12/1953 Parry 112/158 R 3,016,029 1/1962 Card 112/221 X 3,433,189 3/1969 Weisz 112/158 R 3,673,971 7/1972 Ono ll2/l58 R Primary E.\'aminer-Werner H. Schroeder Atmrney-Marshall J. Breen et al.

[57] ABSTRACT A sewing machine, particularly of the zigzag stitch type in which the needle bar gate is pivotably mounted in the frame of the machine and carries a needle bar and needle mounted thereon for endwise reciprocation and vibratory movement transverse to the line of stitches being produced. The penetration of the needle is co-ordinated with the vibratory movement of the needle bar gate by the provision of an eccentric member co-operable with the gate and with a latch member carried by the needle bar, pivotal movement of the gate effectuating'rotation of the eccentric member and linear displacement of the latch member. Means are also provided which co-operate with the latch member for effecting skip stitching.

11 Claims, 5 Drawing Figures SEWING MACHINE WITH HOOK TIMING AND SKIP STITCH MECHANISMS BACKGROUND OF THE INVENTION It has been heretofore recognized that in the operation of an ornamental stitch sewing machine difficulty is occasioned by the fact that as the needle is jogged laterally the timing between the looptaker and the needle is disturbed. This leads to unprogrammed skipped stitches and thereby to a pattern of stitches which may be unsightly and/or deficient in desired strength.

Numerous attempts have been made previously to compensate for this change in timing. One such attempt involved co ordinating the rotation of the looptaker with the endwise reciprocation of the needle such that when the needle was in a neutral position so as to develop a straight stitch, i.e., jogged neither left nor right, optimum presentment of the loop to the looptaker was established. With timing of this character there was a concomitant acceptance of occasional skipped stitches since no compensation was provided for premature looptaking when the needle was jogged in the direction towards the approaching looptaker nor for the late arrival of the looptaker when the needle was jogged in the opposite direction.

Other attempts at minimizing the timing problem involved providing the machine with some form of compensating mechanism whereby the needle penetration was regulated so as to more accurately locate the eye of the needle with respect to the looptaker. Thus, mechanisms were utilized which were intended to compensate for the various jogged positions of the needle such that the eye of the needle would be timed to meet the hook of the looptaker at the proper time and place; U. S. Pat. No. 1,159,523 issued Nov. 9, l9l5,for example, provided a cam groove adapted to receive the lug of a bracked secured to the needle bar. As the needle bar was caused to jog horizontally the lug was caused to ride within the cam groove to thus establish a control for the vertical movement of the needle.

A further and more recent attempt to compensate for the effect of needle jogging upon the timing between the eye of the needle and the looptaker is disclosed in U. S. Pat. No. 2,932,268 issued Apr. 12, 1960 to Ralph E. Johnson.

By the teaching of this patent the depth of needle penetration was regulated, dependent upon the horizontal position to which the needle was jogged, by providing for co-operation between a stud member pivotably secured to the needle bar and the needle bar drive link in which it was slidably mounted. Such stud was also mounted in acute angular relation to the arm shaft. In this manner the depth of needle penetration was increased when jogged to the side away from the appreaching looptaker whereas the depth of needle penetration was decreased when jogged in a direction towards the approaching looptaker.

Although such prior art attempts at compensation achieved varying degrees of effectiveness, extended use of the machine frequently resulted in excessive wear or dislocation of certain elements and less than optimum timing. As a consequence, the number of skipped stitches increased as did the noise level of the machine during operation.

Furthermore, the provision of a compensating mechanism as heretofore described, in order to avoid unprogrammed skipped stitches, was independent of prior attempts to incorporate programmed skip stitching into sewing machines of the ornamental stitch type. The conventional skip stitching mechanism is designed for co-operation with a special skip stitch cam generally positioned on a cam stack and operable through the zigzag drive link for the machine. U. S. Pat. No. 3,559,601 issued Feb. 2, 1971 to Edward J. Tullman is typical of one such skip stitch mechanism. Thus, a need existed for a simplified system of effecting skip stitching utilizable not only with such cam controlled systems but also with systems independent thereof and capable of ready integration with a needle timing mechanism.

SUMMARY OF THE INVENTION It is one object of the invention to provide a zigzag stitch sewing machine in which there is incorporated a needle bar height compensating mechanism of improved durability and enhanced capability of retaining a predetermined timing between the needle eye and looptaker.

It is another object of the invention to provide a zigzag stitch sewing machine in which the penetration of the needle may be accurately correlated with the jogging thereof by utilizing a minimum number of elements, thereby also minimizing the opportunities for causing a change in timing between the needle eye and the looptaker.

It is still another object of the invention to provide a zigzag stitch sewing machine in which a skip-stitch mechanism may readily be incorporated with minimum modification of the machine, such skip-stitch mechanism being co-operable with the needle bar height compensator mechanism.

It is yet another object of the invention to provide a zigzag stitch sewing machine of the character described in which the skip stitch mechanism not only is cooperable with the needle bar height compensator mechanism but may be utilized with skip stitch intelligence record means other than the conventional cam stack systems.

According to the present invention there is provided in a zigzag sewing machine having a frame, a looptaker with a beak movable in a predetermined loopseizing path, a needle, a needle bar carrying said needle and endwise reciprocable and laterally shiftable for zigzagging so as to cause said needle to co-operate with said loop taker beak at any one of a range of different positions along said loop seizing path, driving means for imparting endwise reciprocating movements to said needle bar, a separable coupling selectively interconnecting said needle bar reciprocating means and said needle bar for producing skipped stitches when said coupling is separated, said coupling including a latch member pivotally supported on an eccentric member carried by said needle bar and stud means co-operable with said latch member carried by means associated with said needle bar reciprocating means, and mechanism for imparting lateral shifting movements to said needle bar having means associated therewith co-operable with said eccentric member so as to oscillate said eccentric member in accordance with the lateral shifting movements imparted to said needle bar thereby to correspondingly vary the depth of needle reciprocation.

BRIEF DESCRIPTION OF THE DRAWINGS In order that the invention may be more fully comprehended it will not be described, by way of example,

with reference to the accompanying drawings in which:

FIG. 1 is a head end view of a zigzag stitch sewing machine embodying the present invention in which a portion of the end plate has been broken away;

FIG. 2 is a front view of the head shown in FIG. 1 with a portion of the frame broken away;

FIG. 3 is a perspective exploded view of the needle bar height compensator mechanism and the skip stitch mechanism of the invention;

FIG. 4 illustrates the needle bar in locked relationship with the endwise reciprocation driving means and depicts the relative positions of the eccentric bell crank lug and hinge pin for different jogged positions of the needle; and

FIG. 5 illustrates the needle in different jogged positions in relation to a vertical axis looptaker.

DESCRIPTION OF THE INVENTION Referring to the drawings, and particularly toFIGS. l-3 thereof, there is shown the sewing head ofa zigzag stitch sewing machine. As will be noted from FIG. 1 the frame 1 1 of the machine pivotably supports a needle bar gate 12 by means of bearing and sleeve 13 and bearing 14. Bearing l4-may, for example, be of the pintle type, although, as will be appreciated, other types are utilizable. Bearing 13 is desirably of the spherical type. The gate is formed as generally U-shaped member with upper and lower legs 15, 16 respectively connected by a longitudinally extending bight portion 17. Journaled for endwise reciprocation and slight pivotal movement in gate 12 is needle bar 18. Preferably a pair of spherical bearings 19, 20 are employed for this purpose.

It will be observed that the needle bar is carried by the legs of the gate, and the gate is journaled in the frame of the machine such that the pivotal axis of the gate is inclined with respect to the longitudinal axis of the needle bar and intersects same at the point where the upper portion of the needle bar is journaled in the upper leg of the gate, i.e., at bearing 19. It will also be noted that the loner leg 16 of the gate is carried by bearing 14 at a location which is more remote from its free end than the location of bearing 20 which supports the lower portion of the needle bar therein. One of the advantages of offsetting the bearing locations in this manner is that the needle bar is inclined rearwardly within the machine thereby permitting a lower and more aesthetic machine profile. Another advantage is that an increase in the amplitude of needle bar vibration may be achieved with a smaller angular deflection or pivotal movement of the needle bar gate.

Referring to FIGS. 2 and 3, there is shown the customary arm shaft 21 to which crank 22, carrying crank pin 23, is connected in order to impart endwise reciprocation to the needle bar. Needle bar drive link 24 is pivotably mounted on the crank pin and is formed with a depending extension 25 to which a bifurcated block 26 is rigidly secured. Block 26 is mounted on needle bar 18, to be freely slidable thereon, preferably by being formed with a pair of cheeks in which is journaled a stud 27 which positions the block on the needle bar in freely slidable relation thereto. A latch stud 42 extends from the face of one of the cheeks substantially normal thereto.

Needle bar 18 is also provided with collar 28 which, unlike block 26, is rigidly secured thereto, as by set screw 30. Collar 28 is provided with a hinge pin 29 which extends in a direction substantially normal to the longitudinal axis of the needle bar and is of sufficient length to rotatably accommodate a needle bar release bracket, latch member, and eccentric bell crank, all of which will be hereinafter described. Collar 28 is also provided with a depending projection 31 for a purpose to be described herein. A retaining spring 32 is positioned on set screw 30 and is held in place by means such as a spring clip 33.

Needle bar gate 12 is formed with a camming surface, shown as groove 34, extending generally vertically. A slide block 35 is dimensioned to slidably fit within the groove and is formed with a blind bore adapted to receive lug member 36 which is formed adjacent the periphery of eccentric bell crank 37. The bell crank comprises a disc portion to which said lug member is affixed, an aperture 38 being formed therein of sufficient diameter to permit seating of the bell crank on hinge pin 29 so as to be rotatable thereon. The eccentric bell crank is also formed with a concentric stub extension 39 which is dimensioned to seal latch member 40 snugly thereon. Latch member 40 is elongated and generally key-shaped. A notch 41 is formed in one side of the latch member and is adapted to fit about stud 42 formed on block 26. When so positioned on stud 42 the needle bar is operatively connected to the crank 22 for endwise reciprocation. The retaining spring 32 is so configured as to abut the side of the latch member opposite to that having notch 41 therein and serves to resist inadventant disengagement of the latch member from the stud 42.

Also mounted rotatably on hinge pin 29 is needle bar release bracket 52. This bracket is annular and is provided with a pair of spaced ears 43a and 43b. Ear 43a extends radially from bracket 42 and positioned in the path of a skip-stitch actuating member 44 suitably mounted in the frame of the machine for movement into and out of engagement with ear 43a. Ear 43b also extends radially from bracket 52 but has a turned out projection which protrudes out of the plane of the bracket. The projection abuts the side of the latch member opposite that of retaining spring 32. When ear 43a is acted upon by skip stitch actuating member 44 the bracket is caused to rotate clockwise about the hinge pin thereby forcing ear 43b against the latch member and causing it to overcome the resistance of the retaining spring and to disengage from stud 42. In such event the needle bar is operatively disconnected from its endwise driving means and block 26 simply reciprocates freely until the influence of skip stitch actuating member 44 upon the needle bar release bracket is relieved. Spring clip 53 is employed to retain the release bracket, latch member and eccentric bell crank on the hinge pin. Appropriate means maybe provided for preventing or limiting the descent of the collar 28 and needle bar 18. For example, spring means (not shown) may be provided which restrains collar 28. Further, means are desirably provided, well known to the art, for preventing rotation of the needle bar and thus assuring proper orientation of the needle eye to the looptaker.

As will be understood by persons versed in the art, any suitable intelligence record means may be employed in association with the skip stitch actuating member to establish a particular relationship between completed and skipped stitches. Once the influence of the skip-stitch actuator upon bracket 52 is relieved, the

retaining spring 32 will serve to realign latch member such that it is in the path of the block 26 during the upstroke of the latter. As the block 26 is reciprocated to its upper position stud 42 will engage ramp 45 on the latch member and will cause the latch member to rotate in a clockwise direction until notch 41 seats itself on the stud once again. When so seated the needle bar is again operatively connected to the endwise driving means and the needle bar will carry the needle 46 into stitch forming cooperation with the looptaker 47 of the machine. The depending projection 31 on collar 28 serves to stabilize the needle bar when the block 26 is returned to engage relationship with the needle bar. The projection is dimensioned to fit snugly between the cheeks of block 26.

Referring to FIG. 3 the needle bar gate 12 is shown as having an aperture 48 at approximately the midpoint of the upper leg 15. Such aperture is for slidably accommodating the needle bar and the bearing 19 which further allows for vibratory movement of the needle bar. Aperture 49 adjacent the free end of the upper leg is of sufficient size to receive depending portion 50 (see FIG. 1) ofa zigzag drive link 51 (see FIG. 2) adapted to impart a predetermined pattern of vibratory movements to the needle bar gate and thus to the needle bar.

Referring to FIGS. 3, 4 and 5, in operation, when the gate 12 is in its neutral position and the needle bar is positioned in a vertical plane for developing a pattern of straight stitches (as depicted by the positions of the bell crank lug 36 and hinge pin 29 in solid lines in FIG. 3) the needle will follow the path shown by solid line in FIG. 5. As the needle bar gate is vibrated in a clockwise direction by the zigzag drive link 51 the needle bar will be jogged to the right and the needle will follow the path shown by the dot-dash line in FIG. 5. Simultaneously the slide block 35 will move upwardly within cam groove 34 and the eccentric bell crank will be caused to rotate in a counterclockwise direction about hinge pin 29 by virtue of lug 36 being fitted within the blind bore in the slide block. This results in a raising of the latch member 40 and a consequent elevation of hinge pin 29 and needle bar 18. The end result is an increase in the distance between stud 42 and hinge pin 29 accompanied by a decrease in needle penetration. Thus, as depicted in FIG. 5, the penetration of the needle when jogged right is less than in the neutral or straight stitch position and in this manner the timing between the eye of the needle and the approaching looptaker is maintained.

When the needle bar gate is vibrated in a counterclockwise direction by the zigzag drive link 51 the needle bar will be jogged to the left and the needle will adopt the path represented by the dotted line in FIG. 5. As the gate vibrates, the slide block will be caused to slide down along the cam groove, the eccentric bell crank will be rotated in a clockwise direction and the latch member will be displaced downwardly. A corresponding decrease in distance between the hinge pin 29 and stud 42 results (as shown if FIG. 4 by the dotted line representations of these elements) and the needle penetration is correspondingly increased. Thus, FIG. 5 illustrates the needle penetration as being the greatest of the three positions shown in order to allow for the increased time required by the looptaker to reach the point where the loop may be taken. FIG. 4 shows the three positions for both the eccentric bell crank lug 36 and for the hinge pin 29 and should be viewed together with the relative needle positions depicted in FIG. 5.

It will of course be understood that any means for vi brating the zigzag drive link may be utilized, one such expedient being disclosed in U. S. Pat. No. 2,862,468 issued to Ralph E. Johnson.

It will be understood that various changes in the details, materials, arrangements of parts, and operating conditions which have been herein described and illustrated in order to explain the nature of the invention, may be made by those skilled in the art within the principles and scope of the invention.

Having thus set forth the nature of the invention, what is claimed herein is:

1. In a zigzag sewing machine having a frame, a looptaker with a beak movable in a predetermined loopseizing path, a needle, a needle bar carrying said needle and endwise reciprocable and laterally shiftable for zigzagging so as to cause said needle to co-operate with said loop taker beak at any one of a range of different positions along said loop seizing path, driving means for imparting endwise reciprocating movements to said needle bar, a separable coupling selectively interconnecting said needle bar reciprocating means and said needle bar for producing skipped stitches when said coupling is separated, said coupling including a latch member pivotally supported on an eccentric member carried by said needle bar and stud means co-operable with said latch member carried by means associated with said needle bar reciprocating means, and mechanism for imparting lateral shifting movements to said needle bar having means associated therewith cooperable with said eccentric member so as to oscillate said eccentric member in accordance with the lateral shifting movements imparted to said needle bar thereby to correspondingly vary the depth of needle reciprocation.

2. A sewing machine according to claim 1, wherein said mechanism for imparting lateral shifting movements to said needle bar includes a needle bar gate pivotably mounted in said frame and carrying said needle bar, said means for oscillating said eccentric member comprising a camming surface carried by said gate and said eccentric member being an eccentric bell crank mounted rotatably on said needle bar co-operable with said camming surface and adapted to shift said latch member linearly in response to vibratory movement of said gate to thereby effectuate corresponding variations in the depth of penetration of said needle.

3. A sewing machine according to claim 2, wherein a first collar is secured fixedly to the needle bar and is provided with a hinge pin extending outwardly therefrom, a block being slidably secured to the needle bar and connected fixedly to said needle bar reciprocating means, said block having said co-operable stud means thereon in vertically aligned relationship with said hinge pin, said latch member being carried adjacent one end thereof by said bell crank for pivotal movement about said hinge pin, and said latch member being adapted to releasably engage said stud means to operatively connect the needle bar with its reciprocating means.

4. A sewing machine according to claim 3, wherein said eccentric bell crank comprises a disc portion having an axially extending lug thereon adjacent the periphery thereof and a concentric stub extension adapted to seat said latch member thereon, said bell crank being eccentrically mounted on said hinge pin, whereby said latch member may be pivoted generally axially of said needle bar by rotation of said bell crank about said hinge pin.

5. A sewing machine according to claim 4, wherein the needle bar gate is generally U-shaped and comprises upper and lower legs connected by a longitudinally extending bight' portion, said needle bar being carried by the legs of said gate, said gate being mounted in the frame such that the pivotal axis thereof is inclined with respect to the longitudinal axis of said needle bar and intersects same at the point where the upper portion of said needle bar is carried by said upper leg, the lower portion of said needle bar being carried by said gate at a location closer the free end of the lower leg thereof than the point at which said lower leg is mounted in said machine frame.

6. A sewing machine according to claim 5, wherein said camming surface comprises a generally vertically extending cam groove in the said bight portion of said gate, a slide block being provided for operatively connecting said gate and bell crank by being adapted to ride within said groove and to receive said lug on said bell crank.

7. A sewing machine according to claim 5, wherein a zigzag stitch driving link is operatively connected adjacent one end thereof to the upper leg of said gate at a point closer the free end of said upper leg than the location at which said needle bar is mounted therein, said driving link being connected at its other end to intelligence record means for imparting a predetermined pattern of vibratory movements to said gate and thereby to said needle bar.

8. A sewing machine according to claim 3, wherein a generally annular needle bar release bracket is rotatably mounted on said hinge pin, said bracket having a pair of spaced ears formed on the periphery thereof, one of said ears being adapted for engagement by a skip stitch actuator whereby when so engaged the bracket is caused to rotate and the other of said cars is caused to engage said latch member to disengage same from said second collar, the needle bar thereby being disconnected from its endwise reciprocating means.

9. A sewing machine according to claim 4, wherein said latch member is provided with an aperture therethrough of sufficient diameter to permit seating thereof on the said stub extension of the bell crank, the clearance between the seating surfaces of said latch member and stub extension being sufficiently small such that rotation of said bell crank about said hinge pin in response to pivotal movement of said gate results in substantially simultaneous pivotal movement of said latch member about said hinge pin.

10. A sewing machine according to claim 6, wherein vibratory movement of said gate in a clockwise direction causes pivotal movement of the lower end of said needle bar to a position whereby the needle penetration is decreased, such decrease in needle penetration being co-ordinated with the movement of said looptaker so as to insure optimum presentment of a loop of needle thread to the hook of said looptaker.

11. A sewing machine according to claim 6, wherein vibratory movement of said gate in a counterclockwise direction causes pivotal movement of the lower end of said needle bar to a position whereby the needle penetration is increased, such increase in needle penetration being co-ordinated with the movement of said looptaker so as to insure optimum presentment of a loop of needle thread to the hook of said looptaker. 

1. In a zigzag sewing machine having a frame, a looptaker with a beak movable in a predetermined loop-seizing path, a needle, a needle bar carrying said needle and endwise reciprocable and laterally shiftable for zigzagging so as to cause said needle to co-operate with said loop taker beak at any one of a range of different positions along said loop seizing path, driving means for imparting endwise reciprocating movements to said needle bar, a separable coupling selectively interconnecting said needle bar reciprocating means and said needle bar for producing skipped stitches when said coupling is separated, said coupling including a latch member pivotally supported on an eccentric member carried by said needle bar and stud means co-operable with said latch member carried by means associated with said nEedle bar reciprocating means, and mechanism for imparting lateral shifting movements to said needle bar having means associated therewith co-operable with said eccentric member so as to oscillate said eccentric member in accordance with the lateral shifting movements imparted to said needle bar thereby to correspondingly vary the depth of needle reciprocation.
 2. A sewing machine according to claim 1, wherein said mechanism for imparting lateral shifting movements to said needle bar includes a needle bar gate pivotably mounted in said frame and carrying said needle bar, said means for oscillating said eccentric member comprising a camming surface carried by said gate and said eccentric member being an eccentric bell crank mounted rotatably on said needle bar co-operable with said camming surface and adapted to shift said latch member linearly in response to vibratory movement of said gate to thereby effectuate corresponding variations in the depth of penetration of said needle.
 3. A sewing machine according to claim 2, wherein a first collar is secured fixedly to the needle bar and is provided with a hinge pin extending outwardly therefrom, a block being slidably secured to the needle bar and connected fixedly to said needle bar reciprocating means, said block having said co-operable stud means thereon in vertically aligned relationship with said hinge pin, said latch member being carried adjacent one end thereof by said bell crank for pivotal movement about said hinge pin, and said latch member being adapted to releasably engage said stud means to operatively connect the needle bar with its reciprocating means.
 4. A sewing machine according to claim 3, wherein said eccentric bell crank comprises a disc portion having an axially extending lug thereon adjacent the periphery thereof and a concentric stub extension adapted to seat said latch member thereon, said bell crank being eccentrically mounted on said hinge pin, whereby said latch member may be pivoted generally axially of said needle bar by rotation of said bell crank about said hinge pin.
 5. A sewing machine according to claim 4, wherein the needle bar gate is generally U-shaped and comprises upper and lower legs connected by a longitudinally extending bight portion, said needle bar being carried by the legs of said gate, said gate being mounted in the frame such that the pivotal axis thereof is inclined with respect to the longitudinal axis of said needle bar and intersects same at the point where the upper portion of said needle bar is carried by said upper leg, the lower portion of said needle bar being carried by said gate at a location closer the free end of the lower leg thereof than the point at which said lower leg is mounted in said machine frame.
 6. A sewing machine according to claim 5, wherein said camming surface comprises a generally vertically extending cam groove in the said bight portion of said gate, a slide block being provided for operatively connecting said gate and bell crank by being adapted to ride within said groove and to receive said lug on said bell crank.
 7. A sewing machine according to claim 5, wherein a zigzag stitch driving link is operatively connected adjacent one end thereof to the upper leg of said gate at a point closer the free end of said upper leg than the location at which said needle bar is mounted therein, said driving link being connected at its other end to intelligence record means for imparting a predetermined pattern of vibratory movements to said gate and thereby to said needle bar.
 8. A sewing machine according to claim 3, wherein a generally annular needle bar release bracket is rotatably mounted on said hinge pin, said bracket having a pair of spaced ears formed on the periphery thereof, one of said ears being adapted for engagement by a skip stitch actuator whereby when so engaged the bracket is caused to rotate and the other of said ears is caused to engage said latch member to disengage same from said second collar, the needle bar thereby bEing disconnected from its endwise reciprocating means.
 9. A sewing machine according to claim 4, wherein said latch member is provided with an aperture therethrough of sufficient diameter to permit seating thereof on the said stub extension of the bell crank, the clearance between the seating surfaces of said latch member and stub extension being sufficiently small such that rotation of said bell crank about said hinge pin in response to pivotal movement of said gate results in substantially simultaneous pivotal movement of said latch member about said hinge pin.
 10. A sewing machine according to claim 6, wherein vibratory movement of said gate in a clockwise direction causes pivotal movement of the lower end of said needle bar to a position whereby the needle penetration is decreased, such decrease in needle penetration being co-ordinated with the movement of said looptaker so as to insure optimum presentment of a loop of needle thread to the hook of said looptaker.
 11. A sewing machine according to claim 6, wherein vibratory movement of said gate in a counterclockwise direction causes pivotal movement of the lower end of said needle bar to a position whereby the needle penetration is increased, such increase in needle penetration being co-ordinated with the movement of said looptaker so as to insure optimum presentment of a loop of needle thread to the hook of said looptaker. 